Apparatus for the detection of mastitis in milk animals

ABSTRACT

A method and apparatus are described for detecting mastitis in milk animals. Milk from different teats of the animal is passed through conductivity cells and if the conductance of the milk from one teat is different from that of milk from other teats a mastitis infection is likely. A convenient method of comparing conductances using an electrical bridge is described, as is a suitable conductivity cell.

United States Patent Quayle et al.

1451 May 23,1972

54] APPARATUS FOR THE DETECTION OF MASTITIS IN MILK ANIMALS [72]lnventors: Joshua Creer Quayle, Teesside; Graham Roland Greatrix, SeatonCarew, both of England; Ronald Alan Coombe, Bentley,

Australia [73] Assignee: National Research Development Corporation,London, England [22] Filed: Oct. 23, 1969 [21] Appl.No.: 868,841

51 1111. C1 ..A01j 3/00, A 1 j 5/00 58 Field ofSearch..119/14.14,1415;324/30; 73/194 [56] References Cited UNITED STATESPATENTS 2,837,271 6/1958 Haglund ..3'24/30 x 2,898,549 8/1959 Miller.119/14.1s x

3,374,672 3/1968 Horne ..324/30 B 3,474,330 10/1969 Dauphinee. ..324/

3,512,080 5/1970 Hanson ..324/30 FOREIGN PATENTS OR APPLlCATlONS 610,54510/ 1948 Great Britain ..324/30 650,199 2/1951 Great Britain ..ll9/l4.l5 1,002,416 8/1965 Great Britain ..324/30 B OTHER PUBLlCATlONS G.R. Greatrix, J. C. Quayle and R. A. Coombe, Detection of Abnormal Milkby Electrical Means," J. Dairy Report 1968, -213] pages 213- 221.

Dairy Industries, Rapid Abnormality Indicator," Jan. 1947, pages 35- &48, by J. G. Davis.

The Vetemary Record, Apr. 13, 1968, pages 431- 433 ElectricalConductivity and the Leucocyte Count of Bovine Milk,

BY T. W. A. Little, C. N. Forbes, and D. Forbes.

Primary ExaminerAldrich F. Medbery Attorney-Cushman, Darby & Cushman[57] ABSTRACT A method and apparatus are described for detectingmastitis in milk animals. Milk from different teats of the animal ispassed through conductivity cells and if the conductance of the milkfrom one teat is different from that of milk from other teats a mastitisinfection is likely. A convenient method of comparing conductances usingan electrical bridge is described, as is a suitable conductivity cell.

5 Claims, 4 Drawing Figures APPARATUS FOR THE DETECTION OF MASTITIS INMILK ANIMALS The present invention relates to the comparison of theconductivities of liquid samples, and particularly the detection by suchcomparison of mastitis in cows at a stage early enough to prevent theinfection of other cows, lasting damage to the udder, and reduction inmilk yield.

Mastitis is a disease of the udder, which infects milk animals such ascows, sheep and goats and causes serious losses of milk production. Italmost invariably appears in one quarter of the udder at first, so thatonly the milk from the corresponding teat is infected, and spreadsprogressively to the rest of the udder later.

Many changes in the characteristics of the milk occur when mastitisinfects a cow, eg the chloride content of the milk, its pH, itsconductivity, its opacity, its viscosity, and so on. The cost ofequipment to measure these various parameters varies very widely,likewise the robustness, the ease of keeping the working parts clean andsterile, the ease of comprehending the indication presented, and inconsequence the suitability for use in farming and veterinary practice.

Small changes in conductivity occur during the early stages of thedisease before it becomes sufficiently acute to affect the condition andmilk yield of the cow, or the suitability of the milk for sale. Thereare many other factors which cause parallel changes in the conductivity,such factors as diet, condition of the cow, temperature of the milk whentested, season of the year, and so on. Nevertheless, a definitecorrelation has been found between conductivity, permittivity andpermeability and the progress of infection, but there is a wide spreadof values, due to the perturbations that the other factors introduce.

According to a first aspect of the present invention there is provided amethod of detecting mastitis in milk animals having at least twooperative teats, including obtaining electrical signals dependent on theconductivity of samples of milk from at least two different teats of amilk animal and comparing the signals to detect any differences in theconductivity of the samples.

According to a second aspect of the present invention there is providedapparatus for comparing the conductivities of milk samples, including atleast two sensing means, each adapted to allow milk from a differentteat of a milk animal to flow therethrough during milking and eachsensitive to the conductivity of the milk sample therein, anddifferential measuring means coupled to the sensing means for detectingany differences in the conductivity of the samples.

By comparing the conductivities of milk from teats of the same animalthe effects of the perturbations mentioned above are largely removed.

Each sensing means may include a conductivity cell adapted to receive astream of milk from one or two quarters of a cows udder. Theconductivity cell preferably includes at least two electrodes insulatedfrom one another and the cell may have a cylindrical passageway formilk, whose interior surface is partly constituted by cylindricalelectrodes.

Comparing conductivities presents several problems. For example,inaccurate results will be obtained if ineffective cleansing leavescoatings of fat or milk stone on the electrodes of conductivity cellsforming part of the comparison apparatus. Uniting the electrodes to thesurrounding molding without leaving crevices in which bacteria and soliddeposits can lodge is difficult and tends to make conductivity cellsfairly expensive.

To avoid crevices the insulating material is molded around theelectrodes which are assembled beforehand on a cylindrical mandrel.

Certain embodiments of the invention will now be described, by way ofexample, with reference to the accompanying drawings, in which:

FIG. 1 is a circuit diagram of an embodiment of the second aspect of thepresent invention,

FIG. 2 is a perspective view, part cut away, of a conductivity cell usedin the circuit of FIG. 1,

FIG. 3 is a schematic diagram showing how the conductivity cell of FIG.2 is connected in milking apparatus, and

FIG. 4 is a circuit diagram of a further embodiment of the second aspectof the present invention.

In FIG. 1 a bridge having two ratio arms and two milk conduction arms isshown for comparing the conductivities of milk streams. The bridge isfed from a transformer l with alternating current of a suitable voltageand frequency. and the two ratio arms 2 and 3 have a balancingpotentiometer 4. The detection device is an amplifier 5, and the twoother arms of the bridge are composed of two cells 6 and 7. The milkfrom a pair of teats from a cow flows through the cell 6 and from theother pair through the cell 7. Each cell consists of a pair ofelectrodes 8 separated by an insulator from a central electrode 9, andas the milk flows through the cells, the conductivity of the flow iscontinuously measured by the bridge. Any appreciable departure fromequality of conductivity of the milk is detected by the resultingunbalance of the bridge.

FIG. 2 shows a twin cell assembly for receiving the milk from a pair ofteats of a cow. The cell consists of a housing 10 of plastics materialwith a double inlet from two pipes 11, 12, the pipes each beingconnected to the normal form of teat cup. There is a single pipe towhich the two pipes 11 and 12 connect, and this pipe is coupled to theinterior of the housing 10 through which the milk flows. The electrodes8 are joined together, and the electrode 9 is located between the twoelectrodes 8 and insulated from them. When in use, current flows fromthe central electrode to the other two electrodes or vice versa, and thebridge circuit of FIG. 1 continuously evaluates the conductivity ratiosof the milk streams. The outlet of the housing 10 tilts upwards so as tomaintain the bore of the housing continuously filled with milk.

FIG. 3 shows how the conductivity cell is coupled in milking equipment.In FIG. 3 four teat cups 20 are connected in pairs to the pipes 21 and22 connected to a twin cell 23. Thereafter the milk may either pass toan individual receptacle (not shown) or to a common gathering pipe line25 in which case the milk then passes through a cooler 26 to a storagetank and aspirator 27.

This arrangement described is very simple to operate and requires notechnical skill on the part of an attendant. Since however, it detectsthe onset of mastitis in a particular cow, and since it may be requiredto know which particular teat is affected, the invention can be made tooperate with a bridge circuit having a single conductivity cell,containing milk flowing from one teat only, in each arm as shown in FIG.4. In this bridge the transformer l is connected to ratio arms made upof cells 40, 41, 42 and 43 each cell being filled with milk. A balancingpotentiometer 4 is provided, and by deduction from the output of thebridge by way of the amplifier 5, it can be determined which arm of thebridge has an unusually low resistance. If necessary, milk flow to twoof the teats may be reversed in order to check that if this reversalproduces no different bridge divergence i.e. no change in output of theamplifier then it is the other pair of teats which is effected. Thedirection of divergence of the amplifier, either up or down, indicateswhich of the teats finally is affected.

It is found in practice that the foaming tendency of fresh milk causesinaccuracies if foam enters one or more of the measuring cells. Toovercome this difficulty each cell may be made in the form of a U-tubewith the entry for the milk in one leg of the tube. As the milk enters,and passes downwardly through one leg of the tube, the foam tends tofloat towards the top of this leg The foam-free milk passes through tothe other side of the U-tube when it departs to a common header orreceptacle. There is a small bore pipe communicating between the top ofthe down leg of the tube and the header so as to withdraw air rising inthe down pipe. The measuring cells inserted in the arms of the bridge,are placed in the up pipes where foam-free milk is present.

Where it is found that the four-cell bridge method of detection is noteasy to apply in practice then a single cell bridge may be employed eachof the teats being connected to the single cell in sequence, the teatgiving the lowest reading being the one which is most likely to bediseased. Since, however, the balancing of a bridge of this kind andconnection of the various teats to it in sequence involves some manualskill and interpretation of the readings, this arrangement wouldprobably be more suitable for operation by a veterinary surgeon than byfarmers.

We claim:

1. Apparatus for comparing the electrical conductivities of milk samplestaken as the cow is being milked, including at least two sensing means,each allowing milk from a different teat of a milk animal to flowcontinuously therethrough during milking and each sensitive to theelectrical conductivity of the milk sample therein, a four-armelectrical bridge in which each of at least two of the arms include oneof the sensing means which receive the milk, and means for sensingimbalance in the bridge as an indication of the relative conductivitiesof the milk flowing from the different teats.

2. Apparatus according to claim 1, further including tube means forseparately coupling teats of the udder of a cow individually to thesensing means, and means for aspirating milk from the udder through thesensing means.

3. Apparatus for the detection of mastitis in cows comprising a separateattachment and pipe for each of the four teats of a cow, four electricalconductivity means whose electrical conductance varies in accordancewith the electrical conductivity of milk therein, means for aspiratingmilk from each teat to flow continuously through the respective one ofsaid electrical conductivity means particular thereto, a four-armelectrical bridge in which each bridge arm includes a respective one ofthe electrical conductivity means, and means for sensing imbalance inthe bridge as an indication of the relative con ductivities of the milkflowing through the respective electrical conductivity means from thefour teats.

4. Apparatus as claimed in claim 3, in which each electrode assemblycomprises a body portion of plastics material, defining asmooth-interiored cavity, with electrodes of conducting.non-electrolizable material in the wall of said cavity.

5. Apparatus as claimed in claim 4 wherein the cavity is of U-tubeformation the milk entering one leg of the U and its conductivity beingmeasured in the other leg.

1. Apparatus for comparing the electrical conductivities of milk samplestaken as the cow is being milked, including at least two sensing means,each allowing milk from a different teat of a milk animal to flowcontinuously therethrough during milking and each sensitive to theelectrical conductivity of the milk sample therein, a four-armelectrical bridge in which each of at least two of the arms include oneof the sensing means which receive the milk, and means for sensingimbalance in the bridge as an indication of the relative conductivitiesof the milk flowing from the different teats.
 2. Apparatus according toclaim 1, further including tube means for separately coupling teats ofthe udder of a cow individually to the sensing means, and means foraspirating milk from the udder through the sensing means.
 3. Apparatusfor the detection of mastitis in cows comprising a separate attachmentand pipe for each of the four teats of a cow, four electricalconductivity means whose electrical conductance varies in accordancewith the electrical conductivity of milk therein, means for aspiratingmilk from each teat to flow continuously through the respective one ofsaid electrical conductivity means particular thereto, a four-armelectrical bridge in which each bridge arm includes a respective one ofthe electrical conductivity means, and means for sensing imbalance inthe bridge as an indication of the relative conductivities of the milkflowing through the respective electrical conductivity means from tHefour teats.
 4. Apparatus as claimed in claim 3, in which each electrodeassembly comprises a body portion of plastics material, defining asmooth-interiored cavity, with electrodes of conducting,non-electrolizable material in the wall of said cavity.
 5. Apparatus asclaimed in claim 4 wherein the cavity is of U-tube formation the milkentering one leg of the U and its conductivity being measured in theother leg.